Screw cap

ABSTRACT

A screw cap of plastic material has a cap disk and an outer cap rim located adjacent at a right angle to a circumference of the cap disk. The cap rim has an internal thread for closing a filling and/or removal socket of a container for transporting and storing liquid, and a central bung socket arranged retracted in the cap disk, wherein the bung socket has an internal thread for screwing in a bung plug. The bung plug has a cylindrical threaded sleeve with an external thread for screwing in a threaded bore of the bung plug of the cap, and a sealing end provided with a conical multiple seal of sealing rings which, when the bung plug is screwed in, are pressed against a conical inner sealing surface of a sealing projection located adjacent the threaded bore of the bung socket of the screw cap.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a screw cap of plastic material with a cap disk and an outer cap rim located adjacent at a right angle to the circumference of the cap disk, wherein the cap rim has an internal thread for closing a filling and/or removal socket of a container for transporting and storing liquids, and with a central bung socket arranged retracted in the cap disk, wherein the bung socket has an internal thread for screwing in a bung plug.

2. Description of the Related Art

The screw cap known from EP 0 650 446 B1 of the above-described type for closing the filling socket of a bung drum or the internal plastic container of a pallet container with an outer casing of grate rods or sheet metal have the disadvantage that the sealing ring for sealing the bung plug in the bung socket of the screw cap over time does not ensure the tightness of the bung plug closure due to aging phenomena of the material of which the sealing ring is manufactured, particularly in containers for transporting and storing chemical liquids, so that the sealing ring must be replaced regularly.

SUMMARY OF THE INVENTION

It is the object of the present invention to improve the screw cap of the above-described type with respect to an improved tightness of the bung plug closure, a less expensive manufacture, and lowering of the operating costs of the liquid containers equipped with the screw cap which are used as reusable containers.

In accordance with the present invention, a screw cap with a bung socket which is equipped with a bung socket closure has the following advantages.

By providing the plastic bung plug for closing the bung socket of the screw cap with a conical multiple seal in the form of spaced-apart sealing rings integrally injection molded with the bung socket, wherein the multiple seal is pressed against a conical inner sealing surface of the bung socket when the bung plug is screwed in, an optimum tightness of the bung socket closure is facilitated. In containers with internal pressure, the tightness of the bung plug closure for the bung socket of the screw cap is further improved by additionally increasing the contact pressure of the sealing rings of the conical multiple seal of the plug relative to the conical inner sealing surface of the bung socket caused by screwing in the bung socket as a result of the internal pressure of the container acting on the inner wall of the sealing end of the threaded sleeve of the bung plug provided with the multiple seal. By omitting a sealing ring, which would have to be regularly replaced, the manufacturing costs compared to known screw caps with bung sockets which is closed by means of a bung plug with sealing ring, as well as the maintenance costs for liquid containers which are equipped with a screw cap with the novel bung plug for the bung socket of the cap and which are used as multiple-use containers can be significantly lowered.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of the disclosure. For a better understanding of the invention, its operating advantages, specific objects attained by its use, reference should be had to the drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING In the Drawing:

FIG. 1 is a longitudinal sectional view of a screw cap with a central bung socket which is closed by a bung plug;

FIG. 2 is a detailed view, on a larger scale, of the screw cap of FIG. 1, and

FIGS. 3 and 4 are detailed views, also on a larger scale, of two further embodiments of the screw cap.

DETAILED DESCRIPTION OF THE INVENTION

As shown in the drawing, the screw cap 1 manufactured as an integrally molded piece of plastic material includes a flat cap disk 2, an outer cap rim 3 adjacent at a right angle to the circumference of the cap disk 2, wherein the cap rim 3 has an internal thread 4 for closing a filling and/or removal socket of a container for transporting and storing liquids, as well as an internal rim 5. The internal rim 5 is arranged concentrically to the outer cap rim 3 and forms together with the latter a sealing bed 6 for placing therein a sealing ring for sealing the screw cap 1 on the upper rim of the filling and/or removal socket of the liquid container and serves for stiffening and for a better seat of the screw cap on the container socket.

Arranged retracted in the cap disk 2 is a central bung socket 7 which can be closed by means of a bung plug 8 manufactured as an integrally injection molded piece of plastic material.

The bung plug 8 is equipped with a cylindrical threaded sleeve 9 with an external thread 10 for screwing into the threaded bore 11 of the bung socket 7 of the screw cap 1. The threaded sleeve 9 of the bung plug 8 includes a sealing end 12 which is formed onto a conical multiple seal 13 which is formed by four sealing rings 14 with a rounded-off sealing rim 14 a, wherein the sealing rings are spaced apart from each other by grooves 15 and are arranged concentrically relative to the longitudinal axis 16-16 of the plug and whose diameter 17 decreases in the screwing-in direction a of the bung plug 8.

When the bung plug 8 is screwed in, the sealing rings 14 of the conical multiple seal 13 at the sealing end 12 of the bung plug 8 are pressed against a corresponding conical inner sealing surface 18 of a sealing projection 19 adjacent the threaded bore 11 of the bung socket 7 of the screw cap 1.

In accordance with another embodiment of the screw cap 1, an aerating device or a ventilating end aerating device are integrated into the bung plug 7.

For filling an individual container through the bung socket 7 of the screw cap 1 screwed onto the filling socket of the container, the bung plug 8 is screwed out manually by means of a bung wrench from the bung socket 7 of the screw cap 1 and a pump is connected to the bung socket. When filling a plurality of containers through the bung socket 7 of the container filling socket screwed onto the screw cap 1 in automatic filling installations, the bung plugs 7 are screwed by means of a machine out of the screw caps 1.

The bung plug 8 of another embodiment of the screw cap illustrated in FIG. 3 has a cylindrical threaded sleeve 9 with an external thread 10 for screwing into the threaded bore 11 of the bung socket 7 of the cap 1 and with a sealing end 12 which is provided with a sealing ring 14 formed integrally with the sealing end 12. The sealing ring 14 has a rounded-off sealing rim 14 a which, when the bung plug 8 is screwed in, is pressed against a conical inner sealing surface 18 of a sealing projection 19 located adjacent the threaded bore 11 of the bung socket 7 of the screw cap 1.

The bung plug 8 of another embodiment of the screw cap illustrated in FIG. 4 includes cylindrical threaded sleeve 9 with an external thread 10 for screwing in the threaded bore of the bung socket 7 of the cap 1 and with a sealing end 12 which is provided with a conical sealing rim 20 which, when the bung plug 8 is screwed in, is pressed against the conical inner sealing surface 18 of a sealing projection 19 located adjacent the threaded bore 11 of the bung socket 7 of the screw cap 1.

While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles. 

1. A screw cap of plastic material comprising a cap disk and an outer cap rim located adjacent at a right angle to a circumference of the cap disk, wherein the cap rim has an internal thread for closing a filling and/or removal socket of a container for transporting and storing liquid, and a central bung socket arranged retracted in the cap disk, wherein the bung socket has an internal thread for screwing in a bung plug, the bung plug having a cylindrical threaded sleeve with an external thread for screwing in a threaded bore of the bung plug of the cap, and a sealing end provided with a conical multiple seal comprised of sealing rings which, when the bung plug is screwed in, are pressed against a conical inner sealing surface of a sealing projection located adjacent the threaded bore of the bung socket of the screw cap.
 2. The screw cap according to claim 1, comprising four sealing rings integrally formed at the sealing end of the threaded sleeve of the bung plug, wherein the sealing rings are spaced apart by grooves and are arranged concentrically relative to a longitudinal axis of the plug, wherein the diameters of the sealing rings become smaller in a screwing-in direction of the bung plug corresponding to the conical inner sealing surface of the sealing projection of the bung plug of the screw cap.
 3. The screw cap according to claim 2, wherein the sealing rings have rounded-off sealing rims.
 4. The screw cap according to claim 1, comprising a bung plug with an integrated aerating device.
 5. The screw cap according to claim 1, comprising a bung plug having an integrated aerating and ventilating device.
 6. The screw cap according to claim 1, wherein the cap and the bung plug are injection-molded parts of plastic material.
 7. A screw cap of plastic material comprising a cap disk and an outer cap rim located adjacent at a right angle to a circumference of the cap disk, wherein the cap rim has an internal thread for closing a filling and/or removal socket of a container for transporting and storing liquid, and a central bung socket arranged retracted in the cap disk, wherein the bung socket has an internal thread for screwing in a bung plug, the bung plug having a cylindrical threaded sleeve with an external thread for screwing in a threaded bore of the bung plug of the cap, and a sealing end which comprises a single-piece sealing rings having a rounded-off sealing rim which is pressed against a conical inner sealing surface of a sealing projection located adjacent the threaded bore of the bung socket of the screw cap.
 8. A screw cap of plastic material comprising a cap disk and an outer cap rim located adjacent at a right angle to a circumference of the cap disk, wherein the cap rim has an internal thread for closing a filling and/or removal socket of a container for transporting and storing liquid, and a central bung socket arranged retracted in the cap disk, wherein the bung socket has an internal thread for screwing in a bung plug, the bung plug having a cylindrical threaded sleeve with an external thread for screwing in a threaded bore of the bung plug of the cap, and a sealing end which is comprised of a conical sealing rim which, when the bung plug is screwed in, is pressed against a conical inner sealing surface of a sealing projection located adjacent the threaded bore of the bung socket of the screw cap. 